fix wall compute force

Hello lammps users, I have a problem I need to compute the force and
energy of the fix wall lj126, I am simulating a confined liquid for two
walls and need to compute the force of the wall caused in the atoms that
its the pressure in wall, the force in this case is a global vector but
when I choose the fix to include in the thermo_style only compute the
energy for each wall, someone could help me, I need to include the force
in the thermo_style.

# This script builds a A11 Gallium Phase with MEAM potential
# lattice (Angstrom) a1 = 4.53 a2 = 4.82 a3 = 7.11
# ---------- Initialize Simulation

Ga.meam (74 Bytes)

layer.dat (42.3 KB)

library.meam (9.56 KB)

in.test (1.23 KB)

log.lammps (3.15 KB)

Hello lammps users, I have a problem I need to compute the force and
energy of the fix wall lj126, I am simulating a confined liquid for two
walls and need to compute the force of the wall caused in the atoms that
its the pressure in wall, the force in this case is a global vector but
when I choose the fix to include in the thermo_style only compute the
energy for each wall, someone could help me, I need to include the force
in the thermo_style.

​you get the energy because you request a scalar. to get the force you have
to request a vector or rather the proper vector component. see the fix wall
docs for details.

axel.​

Hello lammps users, I have a problem, anyone know how you could calculate
the depths of MEAM potential for example the Gallium, in the case the
lennard jones potential or stillinger-weber potential, the depths in this
case is an input parameter, but in the MEAM potential, what would be the
strategy for determining at least the scale of the energy. Thanks, I hope
you soon replay.

Best regards
Samuel

A potential energy surface calculation will do.

Use loop command to run a series of single point energy calculations for characterizing the potential energy as a function of bond length or cell size.

Ray

A potential energy surface calculation will do.

Use loop command to run a series of single point energy calculations for
characterizing the potential energy as a function of bond length or cell
size.

or even simpler: use fix move for one atom and don't change anything else.

axel.

Thanks Dr. Alex and Dr. Ray for you help me, I understand but the relative
distance that I have to considered if with respect the initial position of
atom, I would like to determinate an effective pair potential for MEAM,
similar the write_pair command for LJ potential, because I want to
simulate a confined liquid of gallium between to fix wall with lj12-6
potential and
I would be helpful to know the depth of MEAM potential to comparer with
LJ12-6 potential.

Thanks
Samuel

Thanks Dr. Alex and Dr. Ray for you help me, I understand but the relative
distance that I have to considered if with respect the initial position of
atom, I would like to determinate an effective pair potential for MEAM,
similar the write_pair command for LJ potential, because I want to
simulate a confined liquid of gallium between to fix wall with lj12-6
potential and
I would be helpful to know the depth of MEAM potential to comparer with
LJ12-6 potential.

there are two conceptual problems here:

- a wall of 12-6 LJ particles would have a 9-3 LJ potential as functional form.
- MEAM is a manybody potential, so it cannot be easily mapped to a
pairwise additive potential. and the potential depth by itself is less
than half of the information. doing an empirical potential scan is the
best you can do for that.